The invention pertains to fiber optical connectors, and more particularly, to an alignment ferrule for a fiber optical connector made from injection molded plastic having a pedestal projecting from an end surface of the ferrule for receiving and surrounding a fiber, the pedestal being readily removed by polishing, after bonding of the fiber to the ferrule to leave a smoothly polished end surface on the ferrule. In other aspects, this invention pertains to a method of making a plastic ferrule with a raised pedestal at one end and to a method of making a fiber optical connector using an injection molded plastic ferrule with a raised pedestal at one end.
It is known in the art to make a fiber optical connector by securing a fiber optic cable to a ceramic or plastic ferrule. The ferrule is generally cylindrical and has an opening extending therethrough. The opening has a diameter slightly larger than the diameter of the fiber. The fiber, which protrudes from an end of the cable, is inserted through the opening in the ferrule and bonded to the ferrule by use of an adhesive, for example, an epoxy. A drop of epoxy is usually applied to the fiber exterior of the opening to protect the end of the fiber. The end of the fiber protruding from the ferrule and the epoxy is cleaved using a diamond tipped tool. The end of the ferrule is then polished. Epoxy surrounding the fiber adjacent the end of the ferrule causes difficulty in locating the cleave position. The fiber can be severed at different distances from the end of the ferrule. The fiber might undesirably break below the end surface of the ferrule. Since it is difficult to predict how the fiber will be severed after it is cleaved, proper polishing of the ferrule end is a problem.
With a ceramic ferrule, expensive abrasives must be used to grind and polish the end of the ferrule. The cost of the ceramic material in a ferrule and the processing of same is considerably more than the cost of a plastic ferrule and its processing, hence, it would be desirable to utilize a relatively inexpensive plastic. Further, it is desired to automate the process of assembling an optical fiber to a ferrule. Present ferrules of either ceramic or plastic do not have a relatively fixed point of extension of the fiber from the ferrule during assembly and thus do not lend themselves readily to automation.
Runge U.S. Pat. No. 4,512,630 discloses an optical fiber connector utilizing a pair of connectors each having a tiny transparent flexible index matching dome of silicone rubber or equivalent material. The connectors have conically hollow receiving surfaces. The fiber ends are aligned and the domes touch and flex completing the optical connection. It is difficult to break the fiber to achieve a flat and perpendicular end face and thus degradation of the connection between the aligned fibers often results.
An object of the present invention is to provide a molded plastic ferrule for a fiber optic connector having a raised pedestal at one end which is integral with the ferrule, is inexpensive to make and which overcomes disadvantages and deficiencies of prior ferrules.
Another object of the present invention is to provide an injection molded plastic ferrule for a fiber optic connector which includes a raised pedestal at one end having a height at least equal to the diameter of the fiber for facilitating assembly of the ferrule and fiber, with the end of the fiber located closely proximate the end surface of the ferrule, whereby the end of the ferrule can be easily polished to remove the pedestal and form a uniformly polished end surface.
Yet another object of this invention is to provide a molded plastic 2.5 mm ferrule for a fiber optic connector having a raised pedestal adjacent one end surrounding the fiber, for facilitating manufacture of the ferrule with a uniformly polished end surface. Other objects and advantages of this invention will be made more apparent hereinafter.